To some extent, it is "not defective" as you are right, as I assume over 90% of the notebook experiences the same problem. I think they aren't really defective, but its more like a design/production issue. I think they really don't expect the notebook will turn out that loose from the design stage (sometimes production stage and design stage are off sometimes to some degree and I think they did a prototype, everything works out good but never really pay attention to all possible detail) and this notebook works out good 95% of the time, so the person who is in charge of that production department approved and production is good to run. I think what the new macbook pro need is an improvement to the hinge to make it stronger.
To create more friction or design something better in order to keep the screen not move when the system is tilted.